Merge 10.4 into 10.5

1 files changed, 4 insertions, 20 deletions

diff --git a/storage/innobase/trx/trx0i_s.cc b/storage/innobase/trx/trx0i_s.cc
index 82477399552..d3d2b742d84 100644
--- a/storage/innobase/trx/trx0i_s.cc
+++ b/storage/innobase/trx/trx0i_s.cc
@@ -141,12 +141,9 @@ struct i_s_table_cache_t {
 struct trx_i_s_cache_t {
 	rw_lock_t	rw_lock;	/*!< read-write lock protecting
 					the rest of this structure */
-	ulonglong	last_read;	/*!< last time the cache was read;
+	Atomic_relaxed<ulonglong> last_read;
+					/*!< last time the cache was read;
 					measured in nanoseconds */
-	ib_mutex_t		last_read_mutex;/*!< mutex protecting the
-					last_read member - it is updated
-					inside a shared lock of the
-					rw_lock member */
 	i_s_table_cache_t innodb_trx;	/*!< innodb_trx table */
 	i_s_table_cache_t innodb_locks;	/*!< innodb_locks table */
 	i_s_table_cache_t innodb_lock_waits;/*!< innodb_lock_waits table */
@@ -1136,8 +1133,7 @@ Checks if the cache can safely be updated.
 @return whether the cache can be updated */
 static bool can_cache_be_updated(trx_i_s_cache_t* cache)
 {
-	/* Here we read cache->last_read without acquiring its mutex
-	because last_read is only updated when a shared rw lock on the
+	/* cache->last_read is only updated when a shared rw lock on the
 	whole cache is being held (see trx_i_s_cache_end_read()) and
 	we are currently holding an exclusive rw lock on the cache.
 	So it is not possible for last_read to be updated while we are
@@ -1269,8 +1265,6 @@ trx_i_s_cache_init(
 	release lock mutex
 	release trx_i_s_cache_t::rw_lock
 	acquire trx_i_s_cache_t::rw_lock, S
-	acquire trx_i_s_cache_t::last_read_mutex
-	release trx_i_s_cache_t::last_read_mutex
 	release trx_i_s_cache_t::rw_lock */
 
 	rw_lock_create(trx_i_s_cache_lock_key, &cache->rw_lock,
@@ -1278,8 +1272,6 @@ trx_i_s_cache_init(
 
 	cache->last_read = 0;
 
-	mutex_create(LATCH_ID_CACHE_LAST_READ, &cache->last_read_mutex);
-
 	table_cache_init(&cache->innodb_trx, sizeof(i_s_trx_row_t));
 	table_cache_init(&cache->innodb_locks, sizeof(i_s_locks_row_t));
 	table_cache_init(&cache->innodb_lock_waits,
@@ -1303,7 +1295,6 @@ trx_i_s_cache_free(
 	trx_i_s_cache_t*	cache)	/*!< in, own: cache to free */
 {
 	rw_lock_free(&cache->rw_lock);
-	mutex_free(&cache->last_read_mutex);
 
 	cache->locks_hash.free();
 	ha_storage_free(cache->storage);
@@ -1329,14 +1320,7 @@ trx_i_s_cache_end_read(
 /*===================*/
 	trx_i_s_cache_t*	cache)	/*!< in: cache */
 {
-	ut_ad(rw_lock_own(&cache->rw_lock, RW_LOCK_S));
-
-	/* update cache last read time */
-	const ulonglong now = my_interval_timer();
-	mutex_enter(&cache->last_read_mutex);
-	cache->last_read = now;
-	mutex_exit(&cache->last_read_mutex);
-
+	cache->last_read = my_interval_timer();
 	rw_lock_s_unlock(&cache->rw_lock);
 }